學習齲病學需要了解的人

1、Dental Caries,Ouyang Yong Associate professorDepartment of Endodontics and Operative DentistrySun Yat-sen University,岳松齡王滿恩史俊南劉正樊明文,李玉晶王嘉德周學東高學軍凌均棨劉天佳,學習齲病學需要了解的人,,史俊南,劉正,樊明文,李玉晶,周學東,凌均棨,吳補領(lǐng),高學軍,Introduction,

2、Photos of dental caries,,,,,Photos of dental caries,,,,,Photos of dental caries,,,,,'Caries' is Latin for 'rot' or 'rotten'. Dental caries means rotten teeth. Caries is the noun which names the

3、diseaseCarious is the adjective, not 'a caries‘,'a carious area' or 'an area of caries'.,,Dental caries can be defined as,Chronic progressive deconstructive disease of hard dental tissues Bacterial

4、 infected diseases caused by specific bacteriaa reversible multifactorial process of tooth demineralization and remineralization.,Dental caries,Dental caries, a bacterial infection, may be define as a posteruptive patho

5、logical process of external origin, involving the softening of the hard dental tissue and proceeding to cavity formation. This is distinct from the dissolution of the hard dental tissues of an unerupted tooth which is no

6、t dental caries but tooth resorption.,The carious process,a pathological process of localized destruction of calcified tooth tissues by acids produced by organisms. Etiologically caries is considered a multi-factorial d

7、isease, which involves interplay between the host (saliva and teeth) micro organisms (streptococcus mutans), and the substrate (dietary carbohydrate sucrose), with the production of Lactic acid. Dental plaque (Bio-film)

8、 serves as the medium for caries development.,Basic pathological changes,demineralization of inorganic tissues of toothDisintegration of the organic tissues of toothinvolves enamel, dentin, cementum,,Epidemiology of

9、dental caries流行病學,Prevalence rate（患病率）： is the proportion of a population affected by a disease of a condition at one point time. Incidence（發(fā)病率）： is a mesurement of the rate at whi

10、ch a disease progresses the increase or decrease in the number of new cases occurring in a population within the same time period,Measuring caries activity,DMF index,D the mean number of decayed teeth with untreated

11、 carious lesionsM the mean number of teeth which have been extracted and are therefore missingF the mean number of filled teethDMF(T) to denote decayed,missing, and filled teethDMF(S) to denote decayed,missi

12、ng, and filled surfaces in permanent teethdmf(t) dmf(s) similar indices for the primary dentition,Frequency distribution of dental caries according to various tooth location,,,,permanent dentition,Deciduous dentition,d

13、istribution of dental caries according to tooth surface,Occlusal > interproximal >buccal,Caries is world wide in its distribution,The prevalence of dental caries increases with the development of economy

14、 High DMF before 1970 in the industrialized country To decrease after 1970 in the industrialized countryMore prevalence in industrialized than in the third word country

15、Caries experience tends to increase in the developing country and decline in many western countries.Caries experience is higher in urban than in rural communities in developing countries.,Prevalence of dental caries (

16、2019)，special for 12-18Y age groupsis increased significantly （20-40%）In recent 10 years, prevalence of dental caries in primary dentition is increased significantly than the permanent,,Why has caries prevalence dec

17、reased in modern population?,The is possibly attributable to The fluoridation of drinking water, use of fluoride toothpastes and improved oral health A changing pattern of sugar consumptionA decrease in virulence(毒力)

18、of the organsims,,Aetiology of dental caries齲病的病因?qū)W,The organic deposits on the enamel surface,four factors is essential for the initiation of dental caries, namely:,Micro-organism mutans streptococciLactobacilliActin

19、omyces,,Substrate Refined carbohydrates(精制碳水化合物) such as sucrose蔗糖 provide a suitable substrate on which the cariogenic micro-organisms act to produce the acids that lead to dissolution of the hard dental tissuesCaries

20、 experience is influenced by the quantity, quality and especially frequency of consumption of the refined carbohydrate,,Susceptible teeth易感牙The ingestion of fluorides during tooth mineralization leads to the formation o

21、f fluor-apatite in enamel. Its presence in enamel makes the tooth less susceptible to dental caries because it is less soluble in acid than the hydroxyapatite(羥磷灰石) which is normally present in the hard dental tissues,,T

22、ime All the factors should be present for sufficiently long time for the caries process to be initiated.,Definition:,Dental plaque（牙菌斑）,Classification of Dental plaque,supragingival plaque ---

23、--dental cariessubgingival plaque -----periodontal diseases,STRUCTURE OF DENTAL PLAQUE,Plaque on smooth surface Plaque-dental surface Middle layer---- condensed microbial lay

24、er body of plaque The surface layer of plaquePlaque in pit and fissure,Composition of Dental plaque,bacteria which form 50-70% of dental plaque a smal

25、l number of epithelial cells Leukocytes Macrophagesglycoproteins which, together with extracellular polysaccharides, form the plaque matrixmucopolysaccharides (粘多糖) such as gluc

26、ans and fructans(右旋糖) Inorganic components calcium phosphorus fluorides .,MECHANISMS OF PLAQUE FORMATION,The attachment, growth, removal and reattachment of bact

27、eria to the tooth surface is a continuous and dynamic process.,Several distinct processes can be recognized,Absorption of salivary proteins and glycoproteins, together with some bacterial molecules, to the tooth surface

28、to form a conditioning film (the acquired pellicle).—— 獲得性膜的形成non-specific interaction of microbial cell surfaces with the acquired pellicle via van der Walls attractive forces.,Irreversible adhesion can occur if specif

29、ic inter-molecular interactions take place between adhesions on the cell surface and receptors in the acquired pellicle.,,Secondary or late-colonizers attach to primary colonizers (coaggregation共集), also by specific inte

30、r-molecular interactions.,FORMATION AND DEVELOPMENT OF DENTAL PLAQUE,Formation of acquired pellicle and primary aggregationBacteria growth and developmentThe mature of dental plaque,Development,Pellicle formation Mic

31、roorganisms do not attach thermselves directly to the mineralized tooth surface and the teeth are always covered by an a cellular proteinaceous film, the pellicleForms on the “naked” tooth surface within minutes to hour

32、s,Salivary glycoproternsCarbohydratesLipida lesser extent components from the gingival crevicular fluid(齦溝液),Major constituents of Pellicle,Because of its selective nature restrict transportation of irons in and out o

33、f the dental hard tissue. It may play an important modifying role in cariesProvide further protection against demineralization of the enamelModify the number of potential adsorption sites for different bacterial speci

34、esAs the substrate for the microorganisms,Function of Pellicle,microbial colonization,Initial microbial colonizationstreptococcus mutans(變形鏈球菌) accounting for 56% of the total initial microfloraActinomyces

35、 spp(放線菌) a minor proportion gram-negative bacteria(G-),Microbial succession,The initial establishment of a streptococcal flora appears to be a necessary antecedent for the subsequent proliferation of oth

36、er organisms The most striking changed is shift from streptococcus-dominated plaque to plaque dominated by Actinomyces.,,MICROBIAL AETIOLOGY OF CARIES,animal studies micro-organisms are involved in the aetiol

37、ogy of dental caries,cariogenic microorganisms,Streptococcus mutanslactobacillus Actinomyces,Cariogenic properties(致齲菌的特性),they are able to produce acid rapidly from fermentable carbohydrates (acidogenic). They thriv

38、e under acid conditions (aciduric) able to adhere to the tooth surface because of their ability to synthesize sticky extracelluar polysaccharides from dietary sugars,Advanced lesions often have a high proportion of lact

39、obacillidentinal lesions have a diverse micro flora with many Gram positive Gram negative bacteria.Root surface caries was originally associated with Actinomyces spp. but recent studies suggest a similar aetiology to e

40、namel cariesRampant caries can occur in xerostomic patients and in infants fed with high levels of sugar in pacifiers (nursing bottle caries). The plaque contains high levels of mutans streptococci and lactobacilli.,Mic

41、ro-organism and caries,Hypotheses and theory relating to Aetiology of dental caries,,,Chemico-parasitic theory(化學細菌學說),This postulates that oral bacteria act on sugar to produce acid which demineralizes the inorganic co

42、mponent of enamel, resulting in the development of a carious lesion.,Proteolytic theory(蛋白溶解學說),It is thought that the organic component of enamel is first broken down by proteolytic enzymes, opening up path-ways for bac

43、teria to attack the enamel by other processes such as by acid or by chelation.,Chelation theory(螯合學說),This postulates that enamel is demineralized by chelating agents at neutral pH. Protein breakdown products as well

44、 as lactic acid are some chelating agents known to exist in nature.,Auto-immunity theory,In this theory, it is suggested that 'forbidden clones' of lymphocytes attack target cells (odontoblasts) rendering the too

45、th vulnerable to caries attack.,,Four foctors theories,caries,The four circle diagrammatically represent the parameters involved in the carious process. All four factors must be acting concurrently (overlapping of the ci

46、rcles) for caries to occur.,The role of dietary carbohydrate,Nutrition ------ systemic dietary effectsDiet ------ local dietary effects,Caries prevalence is low in populat

47、ions adhering to a primitive way of living and a diet of local products with little sugarA drastic increase in caries is invariably seen when these population “improve”their standard of living and adopt a modern “civil

48、ized”diet with high sugar contentA strong correlation between caries development and sugar consumption,epidemiological studies,Sucrose(蔗糖)------called the arch-criminal in dental caries Monosaccharides ,disaccharides

49、 and of the polysaccharide starch can be fermented to acid by the plaque bacteria Sorbitol（山梨糖） xylitol (木糖醇) -----sugar substitutes used in sugar-free chewing-gumsDietary habits and caries prevalence,Host & too

50、th (susceptible teeth),It was a clinical experience that not all individuals with poor oral hygiene and frequent sugar consumption develop cariesIn the laboratory, extracted teeth exposed to the same acidic buffer chal

51、lenge certainly do not develop artificatial caries-like lesions to the same degree within a short period of time,Tooth morphology: susceptible sitesEnvironment of the tooth: Saliva fluoride,Host & tooth,Tooth mo

52、rphology bacterial plaque is an essential precursor of caries , sites on the tooth surface which favour palque retention and stagnation are particularly prone to decay Saliva under normal conditions, the tooth is con

53、tinually bathed in saliva. It is capable of remineralizing the early carious lesion because it is supersaturated with Ca and P. when salivary buffering capacity has been lost, a low Ph environment is encouraged and persi

54、sts longerFluoride particular interest was the discovery of the association between fluoride concentration in water supplies and prevalence of dental caries in children,,It is evident that the mere existence of the

55、three factors operating together does not result in instantaneous mineral loss therefore a fourth circle is often added to stress the time dimension taken for dental caries to develop,Time,Other factors,AgeSexGeograph